Using side-looking acoustic Doppler current profiler (ADCP) and Doppler radar systems to characterize a convergent surface front

A commercial 300 kHz narrowband ADCP was used in a “side-looking” mode with two beams set parallel to the surface at a depth of 0.6 m. Each beam estimated radial velocities and backscatter intensity from the ship to a range of 120 m. Similarly an experimental X-band, vertically polarized. Doppler radar also estimated the radial velocities and backscatter intensity, of the ocean surface, to a range of 200 m. The two instruments were mounted on opposite sides of the ship and data will be reported from a period when the ship sailed parallel to, and zigzagged across, a surface front. The backscatter data from both systems clearly mapped the location of the front in a consistent manner. The backscatter data from both systems could distinguish between the water types on either side of the front. Both systems measured a strong velocity signal at the front. The ADCP velocities portrayed a definite convergence zone. But the radar velocities portrayed a pattern complicated by surface waves. The incidence angle, relative to the surface, of the ADCP beams was a function of ship´s roll. By using measured rolls, it was found that the ADCP data could be depth sorted allowing a two-dimensional characterization of the front in the upper few meters